JPS61265517A - Length measuring apparatus using charged particle beam - Google Patents

Abstract

PURPOSE:To make it possible to simply measure the average width of a specimen having violent undulation at the end part thereof, by calculating the average value of the measured length values of a plurality of X-scanning lines distributed between markers each having a width in a Y-direction. CONSTITUTION:Not only a cursor Cy1 and dotted lines y3-y5 but also the X- scanning line corresponding to a cursor Cy2 are respectively scanned 10 times on a mask M' by electron beam and the detection signals are stored in a line memory 10. When the signals of sections A1, A2 held between the coordinates X1-X4 of longitudinal cursors Cx1-Cx4 are sent to a controller from CPU, the controller reads the signals of the sections A1, A2 stored in the memory to send the same to an integrator and said signals are added to a second time signal having the same coordinates to be stored in the memory. After 10 times of scannings were finished, CPU calculates a measuring length distance on the basis of the max. values of address signals corresponding to the sections A1, A2 and the coordinates intervals thereof from the memory. In the same way, the distances of lines y3-y5 and the cursor Cy2 are calculated and CPU calculates the average value of the distances of length measuring objects.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention scans a sample using a charged particle beam, displays an image of the sample on a display device based on a detection signal obtained during scanning, and The present invention relates to a device for measuring the length of any part of interest in an image.

[Prior art] A sample is scanned two-dimensionally using an electron beam or the like, an image of the sample is displayed on a display device based on a detection signal obtained during scanning, and length measurement is performed while observing the displayed image. The length of the part to be measured is measured using a marker.

Now, consider a case where the width W of the mask M shown in FIG. 8(a) is to be measured. In the conventional length measuring device, two cross markers 81 and 32 as shown in the figure are displayed as the markers, and the markers S1. S2 was manually aligned exactly with one end of the mask M as shown in FIG. 8(b).

However, it takes time and fatigue to move marker S1.82 accurately manually, and the reproducibility is poor, so as shown in FIG. , E2 is displayed, and this area marker E1
, E2 are moved to positions covering one end and the other end of the mask M, respectively, as shown in FIG. 9(b), and an apparatus has been developed in which the width of the mask M can be obtained only by this movement operation. That is, in this device, the area marker El.

When E2 is positioned as above, area marker E1
After extracting the image signal shown in FIG. 10(a) of the X scanning line R corresponding to the Y-direction center of E2, and slicing this signal to a predetermined level, the image signal shown in FIG. 10(b) is extracted. The waveform is shaped as shown, and the width of this signal is measured using a clock signal. According to this device, the lengths of one end and the other end of the mask M can be measured with good reproducibility by simply moving the marker roughly so that the end of the mask M is covered by the marker. be able to.

[Problems to be Solved by the Invention] For example, when trying to measure the width of a mask M' whose end portion is severely undulating as shown in FIG. El in Figure 11
, E2, the width of the mask M' in the X scanning line R is measured, and in the same figure, the width of the mask M' is measured.
'1, l:i, the width at the X scanning line R' is measured, so there will be a large difference in the measured length values. Therefore, when trying to measure the average width of mask M-, area marks E1, E
It was necessary to manually move the position in the Y direction of No. 2 to a position where the average value could be obtained, which caused a problem in operability.

The present invention makes it possible to measure the length with good re-evaluation with the help of a processing unit without accurately moving the marker, and also solves the problems of the conventional device. It is an object of the present invention to provide a length measuring device using a charged particle beam that can easily measure the average width of a .

[Means for Solving the Problem] Therefore, the present invention scans a sample with a charged particle beam, displays an image of the sample on a display device based on a detection signal obtained with the scanning, and superimposes the image on the image. The first . In an apparatus that displays a second marker and measures the distance between the ends of the sample covered by the first and second markers, one end of the first and second markers in the Y direction The coordinates are Yl.

When the coordinate of the other end in the Y direction is Yl, the average value of the sub-length values in a plurality of X scanning lines having Y coordinate values distributed approximately evenly between Yl and Yl is calculated based on the image signal of each scanning line. It is characterized by comprising means for calculating.

[Example 1 Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a diagram showing one embodiment of the present invention. In the figure, 1 is an electron gun, 2 is a focusing lens that focuses the electron beam EB from the electron gun 1, and 3 is a pair of X and Y deflection coils. 4 is a sample to be measured such as a mask. 5 is a secondary electron detector, 6 is a digital scanning signal generation circuit, 7 and 8 are scanning circuits that convert the scanning signal from the digital scanning signal generation circuit into analog signals and amplified them, 9 is a cathode ray tube, and 9D is a scanning coil. , 10 is an AD converter, and 11 is a line memory.

12 is a memory controller, 13 is an integrator, 14 is a cursor memory, 15 is a cursor memory controller, 16
17 is a bright-up circuit that generates a bright-up signal based on a signal from the cursor memory 14, and 17 is a CPU.
, is is an operation console; 19 is a data display signal generation circuit that has a built-in data display memory and generates a display signal for displaying measurement value data etc. on the cathode ray tube 9 based on a signal from the CPU 17; 20 is a data display signal generation circuit; The output end thereof is a synthesis circuit introduced into the grid 9G of the cathode TA tube 9.

As shown in FIG. 2, the line memory 10 is connected to the -
It has 4096 addresses corresponding to the X-direction scan line, and each address has a depth of 8 bits. Further, the cursor memory 14 is connected to the cathode ray tube 9 as shown in FIG.
4096×409 with a depth of 1 bit corresponding to one screen
It has 6 addresses.

Four horizontal cursors C parallel to the X direction on the screen of the cathode ray tube 9
xl, Cx2. Cx3. Cx4 and two horizontal cursors Cy1. In order to display Cy2, 1 is stored in the corresponding address of the cursor memory 14. As shown in FIG. 4, the operation console 18 has the cursors Cxl, . . . , Cx4. Operation knobs VXI, ~ to control the on-screen positions of Cyl, cyz.

Vx4. Vyl and Vy2 are provided. Furthermore, the operation console 18 has a cursor CV for averaging the measured length values.
1. A key Z for instructing the number N1 of X scanning lines during cy2 and a key for instructing the number Ns of integration for the image signal of 1X scanning lines are also provided.

Next, the present invention will be explained in detail by taking as an example the case where the average width of the mask M- shown in FIG. 11 is measured.

In the above-described configuration, when a start of measurement is instructed from the console 18, a scanning signal is generated from the digital scanning signal generation circuit 6, the electron beam EB scans the sample 4 two-dimensionally, and the detector accompanying this scanning The signal from 5 is supplied to the cathode ray tube 9 as a luminance signal via a combining circuit 20. Therefore, the sample image is displayed on the cathode ray tube 9. At this time, since the scanning signal from the digital scanning signal generation circuit 6 is sent to the cursor memory controller 15, the cursor memory 14 is read out in synchronization with the two-dimensional scanning of the sample 4 by the electron beam EB. The bright-up signal generation circuit 16 generates a bright-up signal based on the signal from the cursor memory 14, and sends the bright-up signal to the cathode ray tube 9 via the synthesis circuit 20.
On the screen, six cursors Cx1. are superimposed on the sample image. ~
．． Cx4. Cyl, CV2 is displayed. Therefore,
Knobs of the console 18 Vxl, ~, Vx4. Vyl
, vy2 is operated, the cursor memory controller 15 is controlled based on a signal from the CPU 17, and the address for writing 1 in the cursor memory 14 is changed, so the position of the cursor displayed on the cathode ray tube 9 is moved. Such knobs Vxi, ~, Vx4. Vy
As shown in FIG. 5, the horizontal cursor Cy1. Cy2 is masked with an appropriate width M-
1 to the Y direction position to be measured. Second vertical cursor Cx1. Cx2 sandwiching one end m1 of the mask M-, and the third. Fourth vertical cursor CX3
．． The other end m2 of the mask M' whose length is to be measured is sandwiched between CX4. At this time, the vertical cursor Cx1.
Cx2. Cx3. The coordinates of Cx4 are Xl.

Let them be X2, X3, and X4. Therefore, after setting the number N1 to 5, for example, and setting the number of integrations NS to 10, for example, using the operation console 18, an instruction is given to start length measurement.

Cursor Cy1. When the coordinate values of Cy2 are Yl and Y2, the CPU 17 moves the cursor Cy1 . (Y coordinate values Y3, Y4 that include y2 and divide the space between both cursors into five equal parts.

Y5 is calculated, and a control signal is sent to the digital scanning signal generation circuit 6 based on the obtained information from Yl to Y5. On the mask amount -, first, the cursor Cy1 is
The electron beam EB scans the X scanning line corresponding to 10 times, and then scans the line corresponding to the dotted line y3 in FIG. 5 10 times in the same manner. y5, cursor Cy2 is scanned 10 times each. Note that the dotted line y3. y
4. Y5 is not actually displayed. As the cursor CVI is scanned for the first time, the detector 5 detects the
), this detection signal is sent to the DA converter 10 and converted into a digital signal, and then stored at an address corresponding to the coordinates of each pixel in the line memory 11. Ru. During the second scan, the line memory 11 receives a detection signal that is substantially the same as that during the first scan.
, X2, X3, and X4 are being sent, and a signal representing an area A1 between the coordinates X1 and X2 and an area A2 between the coordinates x3 and Then, the cursor memory controller 15 reads out the signals of sections AI, A, and 2 stored in the line memory 11, sends them to the integrator 13, adds them to the second signal having the same coordinates, and then reads out the signals in the sections AI, A, and 2 stored in the line memory 11. 11 of these sections AI and A2. Third
When subsequent detection signals are sent from the DA converter 10, addition of the signals is performed in the same manner as in the above case. As a result, when 10 line scans are completed by the electron beam EB, a signal whose S/N ratio has been improved by the 10 signal additions is stored in the address corresponding to the sections AI and A2 of the line memory 11. . When 10 line scans are completed, CPtJ17 reads section A1 from line memory 11.
Read out the signal at the address corresponding to section A2 and find the coordinate X a+ax1 where it takes its maximum value, then read out the signal at the address corresponding to section A2 and find the coordinate X where it takes its maximum value.
maX2 is determined, and further, the distance D1 to be measured on the cursor Cyl is calculated based on the interval between these coordinates. This calculated value D1 is stored in a memory attached to the CPU 17.

In exactly the same way, line y3. Line l, line V5. For cursor Cy2, the calculated values [)3.04, D5
, D2 are obtained. Then, the CPU 17 performs D1 to D5.
A signal representing the calculated value is sent to the data display circuit 19. The data display circuit 19 is a CPU
Data display signal generation circuit 19 based on the signal from 17
generates a data display signal, and this data display signal is sent to the cathode ray tube 9 via the synthesis circuit 20, so that the average value of the width W' is displayed on the cathode ray tube screen as shown in FIG. The data value is displayed.

Also, if you want to measure the local width of the mask M' instead of the average value, use the console 18 to measure the horizontal cursor C.
y1. All you have to do is make Cy2 overlap or make the distance smaller, and in this way you can move the horizontal cursor Cy1. Cy
By adjusting the width of 2, the average width and local width can be arbitrarily measured.

In this way, even if the object to be measured has sharply undulating edges, the average length of the object can be automatically measured simply by roughly setting the position of the marker in the Y direction.

It should be noted that the embodiment described above is only one embodiment of the present invention, and many other embodiments may be adopted.

For example, in the above-mentioned embodiment, the length measurement value data is obtained one by one along the 1X scanning line.
After integrating the image signals obtained when one scanning line is scanned, for example, 10 times, the image signals for 10 times of the second scanning line are further integrated into this integrated signal. After integrating the line image signals, the X coordinates corresponding to the two peaks may be determined, and the average value of the measured length values may be determined based on the X coordinates.

Furthermore, in the above-described embodiment, the present invention is applied to a device that calculates the length measurement value based on the two coordinate values at which the signal peaks, but the length measurement value can be calculated by slicing the signal. The present invention is similarly applicable to devices.

Furthermore, although a pair of vertical cursors are used as markers whose horizontal position and width are variable, frame-shaped markers U1 and tJ2 as shown in FIG. 7 may also be used.

[Effect of the invention] As is clear from the above explanation, the present invention has the following effects:
automatically extracting image signals in a plurality of X scanning lines distributed approximately evenly between markers having a width in the Y direction;
Since the average value of the measured length values on these multiple lines is calculated, even if the end of the measurement object has severe ups and downs, it is possible to easily set the marker position in the Y direction roughly. The width can be measured.

In addition, in the device of the above-described embodiment, the horizontal cursor (,
+1. By simply adjusting the distance of CV2, it is possible to switch between measuring the average width of the sample and measuring the local width.

[Brief explanation of drawings]

Figure 1 is a diagram showing an embodiment of the present invention, Figure 2 is a diagram explaining a line memory, Figure 3 is a diagram explaining a cursor memory, and Figure 4 is a diagram explaining an operation console. FIG. 5 is a diagram showing an example of marker display in the embodiment device shown in FIG. 1, and FIG. 6 is a diagram showing signal waveforms to explain the operation of the embodiment device. 7 is a diagram for explaining another embodiment of the present invention, FIG. 8 is a diagram for explaining a basic conventional device, and FIG. 9 is a diagram for explaining a basic conventional device in FIG. FIG. 10 is a waveform diagram for explaining the operation of the conventional device. FIG. 11 is a diagram for explaining the drawbacks of the conventional device. 1: Electron gun E8: Electron beam 2: Focusing lens 3: Deflection coil 4: Sample
5: Detector 6: Digital scanning signal generation circuit 7.8: Scanning circuit 9: Cathode ray tube 10: AD converter 11 Line memory 12.15
:Memory controller 14:Cursor memory 16:Bright up circuit 17:CPU 18:Operation console 19:Data signal generation circuit 20:Composition circuit M, M': Mask 81, S
2: Cross markers E'1, E2. Ul, U2: Area (frame-shaped) marker Cx1. ~． Cx4. Cyl, CV2:
Cursor Xt, ~, X4, ) laxl, X
max2: X coordinate Y1. ~． Y5: Y coordinate

Claims (3)

[Claims] (1) Scan the sample with a charged particle beam, display a sample image on a display device based on the detection signal obtained with the scanning, and superimpose it on the image so that the position in the X and Y directions can be changed. AtsuteX
and a width in the Y direction, and the distance between the ends of the sample covered by the first and second markers is measured. 1
, when the coordinates of one end of the second marker in the Y direction are Y1 and the coordinates of the other end of the second marker in the Y direction are Y2, in a plurality of X scanning lines having Y coordinate values approximately evenly distributed between Y1 and Y2. A length measuring device using a charged particle beam, comprising means for calculating an average value of length measurement values based on an image signal of each scanning line. (2) A length measuring device using a charged particle beam according to claim 1, wherein the width of the first and second markers in the Y direction is variable. (3) The first marker consists of first and second linear vertical cursors parallel to the Y direction and first and second linear horizontal cursors parallel to the X direction, and the second marker is composed of first and second linear vertical cursors parallel to the Y direction. the third parallel to
, a length measuring device using a charged particle beam according to claims 1 to 2, comprising a fourth linear vertical cursor and the first and second linear horizontal cursors.